苯甲酸壳聚糖酯的合成及抑菌性能研究

壳聚糖与苯甲酰氯进行酯化反应合成苯甲酸壳聚糖酯,研究反应条件对产物的影响,用红外光谱确证其结构,并分析产物的性质和抑菌作用。结果表明,当反应温度为0℃、时间3h、反应物(苯甲酰氯/氨基葡萄糖残基)摩尔比6∶1时,壳聚糖的C6-OH和C3-OH被酰化生成酯,该酯在多种有机溶剂中都具有良好的溶解性;在pH 3.5～7.5范围内,对受试菌种均显示出较强的抑制活性,pH 6.5时,对大肠杆菌的MIC为0.03%,对啤酒酵母的MIC为0.07%。这表明,苯甲酸壳聚糖酯在中性及酸性条件下具有良好的抑菌性。     

对羟基苯甲酸壳聚糖酯的制备、表征和抗菌活性

壳聚糖经氨基保护、与对乙酰氧基苯甲酰氯发生酯化、再水合肼去保护合成得到了对羟基苯甲酸壳聚糖酯。在适宜的反应条件下，对羟基苯甲酸壳聚糖酯酯化度可达130％、得率80％以上。产物经IR分析，酸与壳聚糖之间生成了酯，该酯溶解性略优于对羟基苯甲酸庚酯，而醇溶性显著提高：对大肠杆菌和金黄色葡萄球菌抗菌试验表明，该酯抗菌活性大于对羟基苯甲酸庚酯，更优于壳聚糖。     

壳聚糖及其衍生物的抗微生物活性的研究

本文测定了壳聚糖及其衍生物对细菌、霉菌和酵母的最低抑微生物浓度,并研究了 pH 值、浓度对壳聚糖抑菌活性的影响。结果表明,0.05%的壳聚糖对这三类微生物都有明显的抑制作用,壳聚糖-硫脲-Ag~+在0.0025%的浓度下对微生物就有较强抑制作用,比单体的抑菌范围宽,并且抑菌时间比单体有不同程度的延长,但壳聚糖-硫脲和磺化壳聚糖的抑菌效果却低于单体的;pH 值(pH:3.0～7.0)对壳聚糖及衍生物的抑菌活性没有多大影响。     

对羟基苯甲酸壳聚糖酯合成工艺优化及生物活性评价

本文将常用防腐剂对羟基苯甲酸(p-hydroxybenzoic acid,PA)接枝到壳聚糖(chitosan,CS)上，以改善其应用性能。在惰性气氛下，采用单因素实验以及响应面设计法研究其合成反应条件，并考察其体外抗氧化和抑菌性能。在单因素实验的基础上，通过响应面设计法得到对羟基苯甲酸壳聚糖酯(PA-g-CS)的最佳制备工艺是：PA与CS摩尔质量比为1∶1,Vc添加量为0.20 g,H₂O₂添加量为1.00 g，反应时间为12.0 h。在此条件下，PA-g-CS的接枝量为101.16 mg PA/g，试验结果与模型预测结果相差仅1.64%。体外抗氧化和抑菌实验表明，与CS相比，PA-g-CS的ABTS⁺自由基清除活性和抑菌性能均显著增强，且PA-g-CS的接枝量越高，其抑菌活性越强。该工艺对于PA-g-CS的抗氧化和抑菌性能有明显的优化，PA-g-CS有望应用于活性包装、抗氧化剂和防腐剂等领域。     

壳聚糖对金黄色葡萄球菌抑菌活性的研究

研究了壳聚糖对金黄色葡萄球菌抑菌活性,考察了不同壳聚糖浓度、pH值、金属离子、醋酸浓度对壳聚糖抑制金黄色葡萄球菌活性的影响,并以壳聚糖浓度、pH值、醋酸浓度为因素进行正交试验,确定了壳聚糖对金黄色葡萄球菌抑菌活性的最优条件。实验结果表明,壳聚糖对金黄色葡萄球菌的抑制能力随其浓度的升高而增强;壳聚糖溶于浓度为2%的醋酸溶液时,培养基pH控制在6.0时壳聚糖的抑菌活性最强;金属离子在一定程度上降低了壳聚糖的抑菌活性;这3个因素对壳聚糖的抑菌活性的影响程度为壳聚糖浓度pH值醋酸浓度。     

新型高效低毒食品防腐剂--对羟基苯甲酸酯钠

介绍了新型高效低毒食品防腐剂对羟基苯甲酸酯钠的产品特性、使用安全性、抑菌活性和复配增效效果，讨论了对羟基苯甲酸酯钠的抑菌机理，并与苯甲酸钠和山梨酸钾进行了比较。同时阐述了对羟基苯甲酸酯钠在果蔬汁和饮料领域，特别是在低酸性饮料中的应用前景和开发动态。     

壳聚糖金属配合物对黑曲霉的抑制活性研究

通过观察黑曲霉菌丝体的生长及孢子萌发情况,考察壳聚糖(CS)及壳聚糖锌(CS-Zn)、壳聚糖镍(CS-Ni)的抗真菌性能。结果表明：壳聚糖、壳聚糖锌和壳聚糖镍对黑曲霉孢子萌发和菌丝体生长均具有明显抑制作用,且壳聚糖金属配合物的抑菌效果比壳聚糖本身更强,其中壳聚糖镍最强。壳聚糖镍对黑曲霉的抑菌活性受壳聚糖分子质量、环境pH 值、质量浓度因素的影响较大。分子质量为5kD 的CS 制备的CS-Ni 抗真菌效果最好;CS-Ni 抑菌效果在pH3～7.5 时随pH 值降低而增强;随CS-Ni 质量浓度(0～0.75mg/mL)的增加而增强。     

壳聚糖山梨酸酯的合成、表征及抑菌活性研究

通过2步反应合成了壳聚糖山梨酸酯。第1步,山梨酸在氯化亚砜中回流制备山梨酰氯;第2步,壳聚糖与山梨酰氯在甲烷磺酸的催化下酯化合成了壳聚糖山梨酸酯衍生物。采用红外光谱(FT-IR)和核磁共振氢谱(1H NMR)对衍生物的结构进行了表征。结果表明,壳聚糖的羟基与山梨酰氯发生了取代反应,其氨基仍以游离形式存在。在不同的反应物比例下,制备了取代度(DS)分别为0.44、1.21、1.93的3种衍生物,抑菌实验的结果显示:取代度为1.21的壳聚糖山梨酸酯对大肠杆菌、金黄色葡萄球菌和黑曲霉抑制作用最强,最小抑菌浓度分别为0.125,0.125和0.5 g/L。壳聚糖山梨酸酯的抑菌活性远高于壳聚糖,具备作为防腐剂在食品中应用的基础。     

科学家将壳聚糖、有机酸及其纳米级胶体用于食品抗菌包装材料

据sciencedirect数据库消息,2013年6月《食品控制》(Food Control)刊登一项壳聚糖、有机酸及其纳米级胶体在食品抗菌包装材料中潜在应用的研究。研究人员将低分子量及中分子量的壳聚糖及有机酸(苯甲酸、山梨酸、纳米级苯甲酸-山梨酸胶体)抗菌活性进行对比。研究结果表明,壳聚糖抗菌活性受其分子量的影响,低分子量及中分子量壳聚糖最低抑菌浓度(w/v)分别为0.010%、0.015%,纳米级苯甲酸-山梨酸胶体抗菌活性显著高于其非纳米级胶体。纳米级胶体抗菌剂可以使用更少的抗菌物质达     

固体超强酸催化合成长链尼泊金酯及其抑菌活性的测定

利用沉淀—浸渍法合成易分离、可重复利用的超强固体酸SO~(2-)_4/TiO_2、SO~(2-)_4/Fe_2O_3,将其作为催化剂催化合成尼泊金十一、十二酯,同时测定防腐剂尼泊金乙酯、丙酯、十一酯以及十二酯对金黄色葡萄球菌、枯草芽孢杆菌、李斯特菌、大肠杆菌、肠炎沙门氏菌、啤酒酵母菌、木霉菌的最小抑菌浓度。最佳合成条件为:催化剂为SO~(2-)_4/TiO_2,醇酸摩尔比6︰1,反应时间4.5h,温度130~140℃,催化剂为对羟基苯甲酸量的3.50%,十一、十二酯产率为55.29%,57.02%;SO~(2-)_4/Fe_2O_3作催化剂,醇酸摩尔比为5︰1,反应时间3.5h,温度130~140℃,催化剂为对羟基苯甲酸量的3.00%,十一、十二酯产率为69.14%,72.60%。抑菌结果表明尼泊金乙酯、丙酯、十一、十二酯对以上7种菌均有抑菌性,其中尼泊金十一、十二酯抑菌活性强于尼泊金乙酯、丙酯,且最小抑菌浓度均为0.012 5%。     

Utilization of chitosan for preservation of raw shrimp (Pandalus borealis)

Whole and headless shrimp (Pandalus borealis) were dipped in various concentrations of chitosan solution and stored for 20 days at 4–7°C. The effects of chitosan on microbial proliferation, total volatile bases, nucleotide breakdown, and blackspot formation were monitored over this period. Chitosan showed strong antimicrobial properties inhibiting several microorganisms at concentrations ranging between 0.0075 ‐ 0.01%. The Pseudomonads, however, were very resistant to chitosan requiring much higher concentrations (0.1%) for inactivation. Chitosan reduced the levels of total volatile bases but had no effect on nucleotide breakdown. On the incidence of melanosis, there were no significant differences (p > 0.05) between samples treated with chitosan and the non‐treated samples although blackspot formation was more extensive in whole than headless shrimp. Furthermore, treatment of shrimp with 2% chitosan showed consistently lower incidence of melanosis during storage. The results suggest that chitosan may prove useful as a tool for controlling microbial spoilage of shrimp, but may be limited by its ineffectiveness at controlling melanosis in the postmortem animal.     

Chitosan disrupts the barrier properties of the outer membrane of gram-negative bacteria.

The mode of antimicrobial action of chitosan (polymeric beta-1,4-N-acetylglucosamine) on gram-negative bacteria was studied with special emphasis on its ability to bind to and weaken the barrier function of the outer membrane (OM). Chitosan (250 ppm) at pH 5.3 induced significant uptake of the hydrophobic probe 1-N-phenylnaphthylamine (NPN) in Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium. The effect was reduced (E. coli, salmonellae) or abolished (P. aeruginosa) by MgCl2. No NPN uptake was observed during exposure of the salmonellae to chitosan at pH 7.2. Chitosan also sensitized P. aeruginosa and the salmonellae to the lytic effect of sodium dodecyl sulfate (SDS); such sensitization was not blocked by MgCl2 and was reversible by washing chitosan-treated cells prior to SDS exposure. Chemical and electrophoretic analyses of cell-free supernatants of chitosan-treated cell suspensions showed that interaction of chitosan with E. coli and the salmonellae involved no release of lipopolysaccharide (LPS) or other membrane lipids. However, chitosan rendered E. coli more sensitive to the inhibitory action of dyes and bile acids used in selective media. Highly cationic mutants of S. typhimurium were more resistant to chitosan than the parent strains. Electron microscopy showed that chitosan caused extensive cell surface alterations and covered the OM with vesicular structures. Chitosan thus appeared to bind to the outer membrane, explaining the loss of the barrier function. This property makes chitosan a potentially useful indirect antimicrobial for food protection.     

壳聚糖抗菌抗氧化活性及其在食品保鲜中应用

壳聚糖因其可生物可降解、生物相容好、无毒和具有天然抗菌抗氧化活性,使其成为食品保鲜与防腐研究的热点。本文在壳聚糖结构与抗菌抗氧化活性的基础上,重点概述了近年来壳聚糖在食品保鲜中的应用。     

Antimicrobial activity and physical properties of chitosan–tapioca starch based edible films and coatings

Antimicrobial activity of edible coating solutions based on chitosan and blends of chitosan–tapioca starch with or without potassium sorbate (KS) addition was studied. The agar well diffusion assay showed an antagonist effect on the efficiency of chitosan against Lactobacillus spp. when KS and/or tapioca starch were present. A salmon slice coating assay showed that the chitosan solution was the best coating since aerobic mesophilic and psychrophilic cell counts were reduced, pH and weight loss remained acceptable throughout refrigerated storage, extending global quality to 6-days. Chitosan–tapioca starch based films reduced Zygosaccharomyces bailii external spoilage in a semisolid product but were not effective against Lactobacillus spp. The results suggest that antibacterial action depended on the application technique, due to the fact that chitosan is more available in a coating solution than in a film matrix. Interactions between chitosan–starch and/or KS could affect film physical properties and the antimicrobial activity of chitosan. The addition of chitosan reduced water vapor permeability and solubility of starch films.     

Chitosan: antimicrobial activity, interactions with food components and applicability as a coating on fruit and vegetables

Chitosan has recently gained more interest due to its applications in food and pharmaceutics. Among others, the antimicrobial activity of chitosan has been pointed out as one of its most interesting properties of chitosan.The aim of this study was threefold: (1) the quantification of the antimicrobial effect of chitosan with a deacetylation degree of 94% and a molecular weight of 43 kDa on different psychrotrophic spoilage organisms and food pathogens. (2) The determination of the influence of different food components (starch, whey protein, NaCl and oil) on the antimicrobial effect of chitosan and (3) the investigation of the effects of chitosan coatings on controlling decay of minimally processed fruits and vegetables (strawberry and lettuce). For the first aim several bacteria and yeast were exposed to chitosan concentrations varying from 40 to 750 mg/l. Generally, Gram-negative bacteria seemed to be very sensitive for the applied chitosan (MIC0.006% (w/v)) while the sensitivity of Gram-positive bacteria was highly variable and that of yeast was intermediary (0.01% (w/v)). To achieve the second aim, the media, with one of these components added, were inoculated with Candida lambica (±2 log cfu/ml) and were incubated at 7°C until the yeast reached the stationary phase. Starch, whey proteins and NaCl had a negative effect on the antimicrobial activity. Oil conversely had no influence. For the third aim, the chitosan coating was formed by dipping the products in a chitosan–lactic acid/Na-lactate solution from which the pH was adjusted to the pH of the products. These products were equilibrium modified atmosphere (EMA)-packaged, stored at 7°C and during storage sensorially and microbiologically evaluated. A chitosan coating on strawberries was applicable while on mixed lettuce the chitosan coating was not applicable due to the development of a bitter taste. The microbiological load on the chitosan-dipped samples was lower for both products. The antimicrobial effect of chitosan on lettuce disappeared after 4 days of storage, while it maintained on the strawberries during 12 days.     

Antibacterial effects of chitosan solution against Legionella pneumophila, Escherichia coli, and Staphylococcus aureus

Chitosan has been shown to have antibacterial activities on the growth of a wide variety of bacteria. Chitosan solution has been sold commercially for use as an antibacterial agent. Chitosan solution contains not only chitosan but also organic acids as solvents and desalted Japan Sea Proper Water (dJSPW). We aimed to clarify whether chitosan solution has antibacterial activity against bacteria invading bath water, and then to explore the causative factor among these ingredients. The antibacterial activity of full-strength chitosan solution and of 10(2)- and 10(4)-fold chitosan solution diluted with purified water was studied against Legionella pneumophila serogroups 1 (L. pneumophila SG1) and 6 (L. pneumophila SG6), Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus) for 7 days at 37 degrees C. To clarify the causative factor in the antibacterial activity against E. coli, the antibacterial activities of the full-strength and diluted chitosan solutions for 24 h were examined. L. pneumophila SG1 and SG6, and E. coli could not survive in the chitosan solution or in the 10(2)-fold dilute solution for over a day at 37 degrees C. The cells of S. aureus were found to have decreased more than 2.46 log cfu/ml after 1 day of incubation, not only in the chitosan solutions, but also in phosphate buffer solution as a control. No inhibitory effect of dJSPW on the growth of the bacteria was observed. The antibacterial activity of the chitosan solution was lower compared with those of the organic acids solutions, and it increased with decreasing pH value. We observed the antibacterial activity of chitosan solution against L. pneumophila SG1 and SG6, and E. coli, suggesting it may be due to the decreased pH value derived from organic acids rather than from chitosan itself or dJSPW.     

Application of chitosan-incorporated LDPE film to sliced fresh red meats for shelf life extension

Chitosan lactate was impregnated as an antimicrobial additive into low density polyethylene (LDPE) with different concentrations. The antimicrobial effectiveness was tested with three pathogenic bacteria, specifically Listeria monocytogenes, Escherichia coli and Salmonella enteritidis. Also, these chitosan incorporated films were applied on red meat surfaces to determine the effectiveness of chitosan on color shelf life extension and microbial growth inhibition. Chitosan was exposed to 0.1% peptone water containing the three pathogens in separate tests and inhibited microbial growth a higher levels with increasing concentration of chitosan in the film matrix. Oxygen permeability was not affected by the incorporation of chitosan, while the water vapor permeability increased with the addition of chitosan. Film elongation decreased with the addition of chitosan. When chitosan incorporated films were applied on fresh red meat, microorganisms on the meat surface were not inhibited but significant extension of red color shelf life were observed in refrigerated, sliced red meats.     

壳聚糖/卡拉胶聚电解质复合物的制备及其性能的基础研究

用天然多糖壳聚糖和卡拉胶合成壳聚糖/卡拉胶聚电解质复合物(PEC),探讨了PEC合成过程中的反应机理,考察PEC聚电解质在不同pH缓冲溶液中的稳定性和做药物释放载体的可能性。     

Perspectives for chitosan based antimicrobial films in food applications

Recently, increasing attention has been paid to develop and test films with antimicrobial properties in order to improve food safety and shelf life. Active biomolecules such as chitosan and its derivatives have a significant role in food application area in view of recent outbreaks of contaminations associated with food products as well as growing concerns regarding the negative environmental impact of packaging materials currently in use. Chitosan has a great potential for a wide range of applications due to its biodegradability, biocompatibility, antimicrobial activity, non-toxicity and versatile chemical and physical properties. Thus, chitosan based films have proven to be very effective in food preservation. The presence of amino group in C2 position of chitosan provides major functionality towards biotechnological needs, particularly, in food applications. Chitosan based polymeric materials can be formed into fibers, films, gels, sponges, beads or even nanoparticles. Chitosan films have shown potential to be used as a packaging material for the quality preservation of a variety of food. Besides, chitosan has widely been used in antimicrobial films to provide edible protective coating, in dipping and spraying for the food products due to its antimicrobial properties. Chitosan has exhibited high antimicrobial activity against a wide variety of pathogenic and spoilage microorganisms, including fungi, and Gram-positive and Gram-negative bacteria. The present review aims to highlight various preparative methods and antimicrobial activity including the mechanism of the antimicrobial action of chitosan based films. The optimisation of the biocidic properties of these so called biocomposites films and role of biocatalysts in improvement of quality and shelf life of foods has been discussed.     

壳聚糖及其衍生物与脂肪相互作用的研究

以壳聚糖(CTS)及其衍生物为脂肪吸附剂,花生油为吸附对象,通过模拟人体消化系统做体外实验,考察了3种不同性质的壳聚糖衍生物的脂肪吸附容量,其中羟丙基三甲基壳聚糖季铵盐(HTACC)为强阳离子壳聚糖,羧甲基壳聚糖(CMCTS)为亲水性壳聚糖,十六烷基壳聚糖(CTCTS)为疏水性壳聚糖。结果表明:阳离子壳聚糖优于其他衍生物,平均每克可吸附29g油脂;CTCTS次之,每克吸附25g;CTS可吸附22g;CMCTS最差,仅为16g。以壳聚糖和阳离子衍生物为例,进一步考察了影响壳聚糖吸附脂肪的因素,研究表明:作为溶剂的盐酸溶液的pH和用量均可影响样品的吸脂能力,当样品-盐酸溶液浓度为0.01 g/mL、pH为2时,吸附效果较好。